Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- About the author
- 1 The world of machine communications
- 2 The need for a new standard
- 3 Working in white space spectrum
- 4 Weightless in overview
- 5 The network
- 6 The MAC layer
- 7 The physical layer
- 8 Further functionality
- 9 Network design and capacity
- 10 Application support
- 11 In closing
- Glossary
- Index
6 - The MAC layer
Published online by Cambridge University Press: 05 April 2012
- Frontmatter
- Contents
- Preface
- Acknowledgements
- About the author
- 1 The world of machine communications
- 2 The need for a new standard
- 3 Working in white space spectrum
- 4 Weightless in overview
- 5 The network
- 6 The MAC layer
- 7 The physical layer
- 8 Further functionality
- 9 Network design and capacity
- 10 Application support
- 11 In closing
- Glossary
- Index
Summary
Overview
The function of the medium access layer (MAC) is to share the available radio resource among the many thousands of devices that might wish to access it. As discussed in Chapter 4, the starting point in understanding the Weightless MAC is the design options that were selected as a result of the underlying requirements and constraints. Those that concern the MAC include:
the use of TDD
long time duration frames
super-frame structure with sleep mode.
There is never a clean distinction between MAC and PHY and the MAC must provide PHY-level information to the terminals such as the hopping sequence hence there will be some blurring between this and the next chapter.
Scheduled and contended access
There are two ways that a terminal can obtain resource for communications or that the network can communicate with the terminal. These are scheduled access and contended access. Scheduled access occurs when the network and the terminal have pre-arranged to communicate at a particular time. For example, when transmitting a meter reading, the network and terminal may agree the next time that a reading will be sent and this resource is reserved in advance. Contended access occurs when there is information to send that was not envisaged. For a terminal, contended access requires attempting to gain radio resource to signal a desire to communicate. For the network it requires the base station controller making space within a downlink frame to carry the traffic.
- Type
- Chapter
- Information
- Understanding WeightlessTechnology, Equipment, and Network Deployment for M2M Communications in White Space, pp. 74 - 101Publisher: Cambridge University PressPrint publication year: 2012